To date, various underground shelters and underground rooms have been suggested. The underground shelters and underground rooms are common in that a space is provided underground but require different concepts regarding the structures depending on the objectives thereof. Generally, underground rooms are used as a room for hobbies and entertainment (e.g., audio room, music lessen room, living room, bed room). Thus, such underground rooms are required that can be built with a shorter work period and with a lower cost within a range which satisfies legal conditions for a residential underground room. There has been a tendency where this point has been prioritized as a development subject. On the other hand, the first objective of the underground shelter is to safely protect persons or articles therein from various assumed risk factors from the outside. Thus, the underground shelter has been required to have a simpler and sturdier structure and an expert security structure against risk factors.
An underground shelter disclosed in Japanese Unexamined Patent Publication No. 2005-240452 (Patent Document 1) has a main body structure in which a pressure-tight base supported by a plurality of piles driven in the ground has thereon a box-like shelter inner shell made of high-strength concrete. An outer surface constituting a wall and a ceiling face except for the bottom face of the shelter inner shell is covered by the shelter outer shell made of an iron plate. The outer surface of the iron plate, and a space between the bottom face of the shelter inner shell and the pressure-tight base is covered by the waterproof coating.
An underground room disclosed in Japanese Unexamined Patent Publication No. 78609/1997 (Patent Document 2) has a main body structure in which the outer surface of a core member such as a section steel is fixed with a metal plate, the interior of the core member is fixed with a non-metal-base inner plate to form a floor panel, a wall panel, and a ceiling panel. By the use of these panels, there is formed a box-like unit which has a double housing type rigid-frame structure in the short side direction and an earthquake-resistant wall structure in the long side direction. These units are provided and are joined to provide a building frame. The entire area of the outer surface is covered by an organic solvent coating, a synthetic resin coating, and a synthetic resin mortar.
An underground room disclosed in Japanese Unexamined Patent Publication No. 21916/1999 (Patent Document 3) has a main body structure in which a floor section is composed of a base slab made of reinforced concrete, a wall section is composed of a steel-made wall panel, and a ceiling section is composed of a steel-made roof panel. The underground room is particularly characterized in that the lower end of the steel-made wall panel is buried in the concrete of the base slab.
An underground room disclosed in Japanese Unexamined Patent Publication No. 21917/1999 (Patent Document Publication 4) has a main body structure in which a floor section is composed of a steel-made floor panel or reinforced concrete, a wall section is composed of a steel-made wall panel, and a ceiling section is composed of steel-frame beam and a wooden board, or concrete or reinforced concrete. The wall panel is subjected to corrosion-resistant and rust prevention processings and a backfilling by providing a concrete wall on the outer surface of the steel-made wall panel.
[Patent Document 1] Japanese Unexamined Patent Publication No. 2005-240452
[Patent Document 2] Japanese Unexamined Patent Publication No. 78609/1997
[Patent Document 3] Japanese Unexamined Patent Publication No. 21916/1999
[Patent Document 4] Japanese Unexamined Patent Publication No. 21917/1999